Molded electrical insulator



Dec. 21, 1965 M, G, KNOY 3,225,133

MOLDED ELECTRICAL INSULATOR Filed July 3l, 1964 l/ V I ff ff INVENTOR.

- Dec. 21, 1965 M G, KNOY 3,225,133

MOLDED ELECTRI CAL INSULATOR Filed July 31, 1964 3 Sheets-Sheet 2 f u!! llmllwllllf I NVEN TOR.

Dec. 21, 1965 M, G. KNoY 3,225,133

MOLDED ELECTRICAL INSULATOR Filed July 3l, 1964 3 Sheets-Sheet 5 INVENTOR United States Patent O 3,225,133 MLDED ELECTRCAL INSULATOR Maurice G. Knoy, West Lafayette, Ind., assignor t Rostone Corporation, Lgfayette, Ind., a corporation of Indiana File-d July 31, 1964, Ser. No. 386,562 28 Claims. (Cl. 174-212) This invention relates to electrical insulators for supporting electrical conductors, and especially to rigidmounting insulators of molded composition which may be molded without inserts and which have good electrical characteristics and have good strength and other physical properties.

It is a principal object of the invention to provide molded insulators, and especially those of the type used for rigidly mounting conductors on fixed supports, which need not necessarily contain molded-inserts for fastening the conductor to the insulator or the insulator to its support, but which can be secured to the conductors and to supports by means of conventional bolts engaged in conventional nuts or other threaded fasteners which are received and held in formed pockets in the insulator. It is a further object of the invention to provide such a molded insulator which has good electrical and physical properties, which will be readily moldable of compositions which have good insulating properties, which may have non-tracking and arc-quenching characteristics, and may include strengthening fibrous reinforcement; which by its configuration will provide convenient mounting pads and adequate physical strength, will electrically separate and shield the attached conductive elements from each other to avoid flash-over arcing, and will provide a long over-surface length to avoid surface leakage; and which by reason of these superior properties will meet high electrical and physical requirements and satisfy severe test specifications, such as the electrical and physical performance standards of the National Electrical Manufacturers Association (NEMA) specifications for high voltage kv.) stand-off insulators. It is an object of the invention to provide such electrical insulators which will have a configuration and wall thickness which will make them readily moldable from advantageous molding compositions by convenient and economical molding processes, including both compression molding and transfer molding processes. It is a further object of the invention to provide such molded insulators which are adapted to be molded of synthetic resins, such as polyester, epoxy, and other synthetic resins, and of such materials which may contain effective proportions of reinforcing fibrous material, such as glass fiber, and of cornponents which give non-tracking characteristics.

In accordance with the invention, the electrical insulator comprises a one-piece molded body which provides end plates forming outwardly-disposed mounting pads or seats, interconnected and held in spaced relationship by strut walls extending between the end pla'tes and providing load-bearing strength against axial, torsional and bending stresses. The end plates are provided with bolt holes to receive fastening bolts and with nut-receiving inner faces :or seats about such holes, and the body walls form pockets or housings to receive, enclose, and hold the nuts for the fastening bolts. Each nut pocket opens laterally to permit insertion of a nut from the side, while the pocket walls extend laterally about and beneath each nut to electrically shield it from the conductive elements at the opposite end of the body. The insulators may include, and those which are to be used as high-voltage insulators preferably do include, a barrier plate or wall interposed between the nut pockets and mounting pad 3,225,133 Patented Dec. 2l, 1965 at one end `of the insulator and those at the other end of the insulator.

The end plates are desirably circular, but may be square or other shapes, as desired. The strut walls are formed to carry axial bearing loads, and therefore include portions which are straight in the direction between the end plates. For strength against bending and torsional stress, the strut wall structure preferably includes interconnected walls or wall portions which are disposed and joined in an angular relationship. A desirable strut configuration includes integrally joined walls in intersecting straight or curved planes. The shape used may be chosen to give high strength, convenient molding, and good electrical characteristics, such as a long over-surface length and adequate electrical barrier shielding, and to provide drainage and avoid the collection -of moisture in critical areas which would shorten the over-surface length. A preferred strut configuration which gives especially high strength in combination with other desired characteristics comprises a central tubular wall integrally joined to a plurality of radially-disposed reinforcing walls, with the nut pockets aligned with or closely adjacent to the reinforcing walls and closely adjacent to the tubular wall. ily molded in a two-part mold with retractable end inserts to form the bolt holes and the hollow core of the tubular wall.

Another desirable configuration, which provides adequate strength for many applications, comprises integrally-joined strut walls in two intersecting planes, desirably a cruciform or X-form, which provide a plurality of intersecting radial walls. Other desirable configurations include Y-shapes, star or spider shapes, H-shapes, and T-shapes. Curved shapes may also be used, for example, shallow C and S-shapes.

An interposed barrier wall serves primarily as an electrical barrier between conductors at the opposite ends of the insulator, and preferably extends transversely between the opposite ends. It is preferably of the sanne shape as the end Walls and positioned parallel to and midway between such end plates. Other sizes, shapes, and positions may also be used and may be desirable under certain circumstances. For example, an oblique wall may serve both as a reinforcing strut wall and also as a barrier between nut pockets located on opposite sides of the oblique wall.

The number and positions of bolt holes may be varied. A preferred arrangement is to provide two bolt holes at one end of the insulator and four at the other end of the insulator, which permits the insulator to be used to mount a conductor either parallel with or at right angles to a support.

The nut pockets are preferably made of a size to readily accept manually-inserted nuts, and to hold the nuts against rotation, and may be shaped to receive either sqaure or hex nuts. The pockets open laterally, that is, to the side of the insulator and they may be relatively deep for the purpose of lengthening the electrical path between the nut and a conducting element at the opposite end of the insulator. They may be formed as transverse rectangular pockets closed at one end and open at the other, or as openings extending across the insulator and open at both ends. The pockets may have nut-positioning stops at one end, and pockets with closed ends may be provided with drain openings if desired.

While the full advantages of the invention are obtained when nuts and bolts are used at all fastening points of the insulator, it is also possible to use molded inserts at certain fastening points and nuts and bolts at other fasten- 1ng points.

The accompanying drawings illustrate the invention. In such drawings:

This configuration can be read- FIG. 1 is a front elevation of an insulator embodying the invention and positioned as a rigid mounting between a xed support and a conductor;

FIG. 2 is a front elevation on an enlarged scale, of the insulator shown in FIG. l;

FIG. 3 is a side view of the insulator of FIGS. 1 and 2;

FIG. 4 is a top view of the insulator of FIG. 2;

FIG. 5 is a bottom view of the insulator of FIG. 2;

FIG. 6 is a sectional view on the line 6-6 of FIG. 2;

FIG. 7 is a sectional view on the line 7-7 of FIG. 2;

FIG. 8 is a sectional view on the line 8-8 of FIG. 2;

FIG. 9 is a partial section, taken on the line 9-9 of FIG. 2, to which is added a side elevational view of a manually-inserted self-retaining nut in the nut pocket;

FIG. 10 is a sectional View of a modified construction, taken as though on the line 9 9 of FIG. 2, but with the nut-stop removed and with a dual nut fitting inserted;

FIG. 11 is a front view of a modified insulator embodying the invention',

FIG. 12 is a side view of the insulator of FIG. l1;

FIG. 13 is a top view of the insulator shown in FIG. 11, with the right half of the figure broken away and shown as a sectional View taken on the line 13-13 of FIG. 11;

FIG. 14 is abottom view of the insulator of FIG. 11;

FIG. 15 is a side view of a further modified form of insulator embodying the invention;

FIG. 16 is a sectional view taken on the line 16-16 of FIG. 15;

FIG. 17 is a front view of a further modification; and

FIG. 18 is a side view of the lower end of the insulator of FIG. 17.

The insulator shown in FIGS. 1-9 comprises a molded one-piece body 10 which, as indicated in FIG. l, is adapted to be bolted to a fixed support 12 and to have a bus bar or other electrical conductor 14 bolted to its opposite end. The molded body 10 may be made from any of a number of desirable molding compositions of the type and character commonly employed in molding electrical insulating parts. Preferred compositions include those containing from 10% to 50%, and preferably from 20% to 35%, of a resin binder such as polyester, epoxy, melamine, and other synthetic resins; an effective proportion, say 10% to 20%, of glass fiber or other fiber reinforcement; and from to 80% of hydrated alumina, which gives non-tracking and arc extinguishing properties. These are represented by the following:

Molding composition I Ingredient: Percent by weight Polyester resin binder 25 Glass fiber reinforcement 15 Hydrated alumina 60 Molding composition Il Ingredient:

Epoxy resin, polymer and monomer 25 Gla-ss liber 15 Hydrated alumina 60 The molded body 1t) is of substantially uniform wall thickness throughout, so that it provides rapid and uniform curing without internal strains.

In the insulator shown in FIGS. 2-9, the body 10 comprises a top end plate 1.6 and a bottom end plate 18 which form mounting seats on their outer faces and which are interconnected by strut walls. The strut walls include a central cylindrical wall 20 and two rectangularly disposide radial walls 24 and 26 integrally joined thereto, all extending normal to the end plates 16 and 18. The cylindrical wall 20 defines two hollow cavities 21 and 22 opening at the opposite ends of the body 10 and separated from each other by a common bottom wall 23. As shown, the top cavity 21 is circular at its lower end but generally square at its top end, the squareness being used to provide side walls 29 of uniform thickness between the central cavity 21 and the nut pockets described below. Similar squareness is not needed for the bottom cavity 22 because of the presence of the through opening forming the second pair of nut pockets.

As shown, the plates 16 and 18 are circular, but square or other shapes can be used. Between the end plates 16 and 18, the strut walls carry a barrier plate 30, which is preferably circular in shape and interposed midway between the end plates 16 and 18, as shown; but other shapes and positions can be used which provide the desired electrical barrier effect between the conducting elements at opposite ends of the insulator.

To provide for drainage from the pockets defined by the above described plates and walls, drain holes 32 are formed through the wall 24 close to its intersection with the cylindrical wall 20 and the barrier plate 30.

As shown in FIG. 4, the top end plate 16 is provided with two bolt holes 34- which lead through the plate 16 to nut enclosures or pockets 36 which extend parallel to the strut wall 26. The pockets lie between the cavity walls 29 and outer side walls 38 and are defined by such walls and by bottom walls 40. The bottom wall 40 may have a thickened central portion into which the bolt hole 34 is extended for clearance of the inner end of the bolt used. Each nut pocket 36 is open at one end, and closed at the opposite end by a wall 42 which forms a nut-positioning stop having a central groove to receive hex nuts and flat anks to receive square nuts. As will be seen in FIG. 3, the nut pockets 36 desirably open in the same direction, and their walls 38 and 4t) are relatively short transversely of the insulator, with their ends spaced inward from the edges of the strut wall 26.

As indicated in other modifications, the nut pockets used at both the top and bottom of the insulator may have drain openings at their inner ends or may be fully open at both ends, but the arrangement of FIGS. 2-8 is preferred.

As is shown in FIG. 5, the bottom end plate 18 contains four bolt holes. Two bolt holes S4 are aligned with the bolt holes 34 in the top plate 16, and the axes of these four bolt holes lie in the central plane of the strut wall 24. Each bolt hole 54 leads to a nut pocket 56 defined by inner and outer side walls 58 and a top wall 60 which is centrally thickened to receive a bolt hole extension. The nut pockets 56, like the pockets 36, are closed at one end by walls 62 which form nut-locating stops, and such stop walls are at the opposite ends of the Apockets 56 from the walls 42 of the pockets 36, so that the pockets 36 and 56 open in opposite directions. See FIG. 3 and FIGS. 6-8.

The other two bottom bolt holes 55 are displaced 90 from the bolt holes 54, about the axis of the insulator body 10, and lie on the central plane of the strut wall 26. Such bolt holes 55 lead to nut pockets 57 which lie between the bottom end plate 1S and transverse walls 61 and are defined at the sides by side walls 59. Such side walls 59 are desirably integral with the inner side walls 58 of the side nut pockets 56 and with them define a continuous opening diametrically through the insulator body. Nut stops may be formed either by offsets between the walls 59 and 58, or by central webs 63 as shown between the nut pockets 57 and the cavity 22. The nut-stop web may be shaped like the nut stops 42 and 62, with central grooves and fiat flanks to position either hex nuts or square nuts in the nut pockets 57. The openings 65 beside the webs 63 serve as drain openings for the nut pockets 57 and provide proper section thickness in the walls 58.

The walls of the insulator body I0 are all of substan- ,tially the same thickness and substantially uniform throughout, to facilitate molding and to give uniform and on the body may be rounded to facilitate mold formation and avoid stress concentrations. The body 1G of FIGS. 1-8 is adapted to be molded in a two-part permanent mold which parts in the center plane of the strut Wall 24 and is provided with suitable retractable end inserts to form the cavities 21 and 22. The bolt holes are also desirably formed by retractable mold inserts, but could be bored.

Use of the insulator of FIGS. 1-8 is illustrated in FIG. 1. As shown, the bottom end plate 13 is used as the base and is bolted to a fixed support 12, by a pair of bolts 66 threaded into nuts 67 in the pockets 56. The upper end plate 16 supports a bus bar or other conductor 14 which is bolted to the insulator by a pair of bolts 68 passed through the conductor and the bolt holes 34 and threaded into nuts 69 in the pockets 36. The pockets are shaped to position the nuts in alignment with the holes and to hold them from turning so that the workman simply inserts the nuts manually into the pockets and screws the bolts into them. As shown, the support 12 and conductor 14 extend in the same direction so that the bolts 66 and 68 are all in the same plane. The additional bolt holes 55 in the bottom end plate 18, however, permit the insulator to be mounted on a support running at right angles to the conductor.

The insulator of FIGS. 1-8 fective insulator. It has high physical strength against axial, torsional, and bending stresses, adequate to meet the demanding NEMA performance standards for highvoltage insulators. Its configuration provides electrical Hash-over spacing and over-surface distances adequate to meet the electrical requirements of such high-voltage insulators. It accomplishes these results within the size and spacing limitations of industry standards. It also avoids the need for molded-in inserts for mechanical attachment, and permits the use of conventional bolts and nuts of standard sizes, and utilizes such fasteners in a manner which gives the desired superior physical and electrical characteristics.

The relationship is such that the electrical discharge distance, both through air and over the surface, from the bolts and nuts at one end to conductive parts at the other end of the insulator is substantially equal to or greater than the electrical discharge distance between the conductive elements, i.e. the bus bar 14 and the support 12, between which the insulator s positioned. Consider, for example, the nut in an upper nut pocket 36 of FIGS. 1-8. The electrical discharge path through air extends first from the nut to the open end of the pocket 36, thence outward and downward about the barrier plate 30, and thence ordinarily to the support 12. It is farther to the nuts in the pockets 56 and S7, especially since the pockets 56 open oppositely from the pockets 36 and the pockets 57 are relatively deep and are angularly displaced from the point at which the path crosses the barrier 3u. The shortest path from a nut at one end to a conductive part at the other end is probably from a nut in a pocket 57 at the bottom of FIG. 3 to the bus bar at the top of the insulator, for the air path then extends from the nut out to the open end of the pocket, and thence upward past the barrier plate 30 directly to the bus bar. Because of the depth of the pocket 57, this air path distance is substantially as long as the direct path distance between the bus bar and support at opposite ends of the insulator` The over-surface distances are likewise long. For example, the shortest over-surface distance directly between the bus bar and support in FIG. 1 follows the profile of the insulator as shown in FIGS. 1, 2, or 3; and the oversurface distance to any of the nuts is substantially the same or longer.

In FIG. 1, the nuts and bolts shown are conventional nuts and bolts of a standard size. For convenient handling, and to increase surface area contact with the molded insulator and reduce unit pressures, the bolts and unts provides a sturdy and efused are desirably larger than would be needed for stress requirements in the bolts and nuts themselves. The nut pockets are shaped to loosely receive such conventional nuts of standard sizes, either square nuts or hex nuts, and to hold the nuts against rotation as the fastening bolts are threaded into them. Where nut stops are provided, as by walls 42 and 62, and the webs 63, the nuts are easily inserted manually through the open ends of the nut pockets, and may be held in place with the finger until the bolts are suitably engaged in the nuts. Where the nut pockets are open at both ends, such as in the case of the nut pockets in FIGS. 17 and 18, it is readily convenient to insert the nuts in the nut pockets and hold them between the thumb and forenger while the fastening bolts are engaged with them.

Instead of standard square or hex solid nuts, various other conventional or special nut-like fasteners may be used, and the nut pockets may be shaped to receive such special fasteners. Also, instead of providing a loose fit of the nuts in the pockets, the nuts may have a self-retaining engagement with the nut pockets. FIG. 9 shows a formed sheet metal nut 8f) fitted in a nut pocket 57. The nut is generally U-shaped, and has a bottom leg 82 which is punched and threaded, and a top leg 84 which is punched to pass the bolt. Nuts of this general type are available on the market and have adequate strength and holding power for many applications of the insulator of this invention. The legs 82 and 84 of such units are yieldable so that the nuts can be made to frictionally retain themselves in the pockets. As shown, the leg 84 of the nut 811 is deformed to provide a retaining lip which locks into the upper extension of the bolt hole 55.

In FIG. 10, the webs 63 between a pair of nut pockets 57 have been omitted (or knocked out) and a dual nut fitting 86 is inserted in the through hole thus provided. Such fitting S6 is generally hat shaped, with formed end portions S7 which provide nuts for the two bolts holes 55, and a raised center portion SS which interlocks with the wall of the cavity 22.

Self-retaining inserts can be readily inserted in the finished moldings without the trouble and expense of molding them in place, and at substantially less cost. The resulting insulators may be sold with inserted nuts in place and will be fully equivalent to, and used in the same manner as, prior insulators in which the fastening inserts were molded in place in the insulator body.

The modification shown in FIGS. ll-l4 omits the cylindrical strut wall of FIGS. 1-8 and is a somewhat simpler molding. While this difference reduces maximum bending strength slightly, the physical properties are ample for most applications. The insulator of FIGS. 11-14 comprises a body 110 having a top end plate 116 and a bottom end plate 118 interconnected by strut walls 124 and 126 arranged in cruciform relationship and disposed in intersecting diametric planes at right angles to each other and normal to the end plates 116 and 118. The end plates 116 and 118 are circular, but square or other shapes can be used. Midway between the end y plates, the strut walls 124 and 126 carry a barrier plate 136, also circular in shape. Drain holes 132 are formed through the wall 124 close to its intersection with the wall 126 and the barrier plate 13).

The top end plate 116 has two bolts holes 134 which lead through the plate 116 to nut pockets 136 parallel to the strut wall 126. The pockets are defined by short side walls 1?7 and 138 depending from the end plate 116 and by bottom walls 140. Each nut pocket 136 is open at one end, and is partially closed at the opposite end by a nut stop 142 flanked by a pair of drain openings 144. The stops 142 are desirably at the same ends of the two pockets 136, and are shaped to fit either square or hex nuts.

The bottom end plate 118 contains four bolt holes. Two bolt holes 154 are aligned with the bolt holes 134 in the top end plate 116, and lie in the central plane of the strut wall 124. Each bolt hole 154 leads to a nut pocket 156 defined by inner and outer side walls 158 and a top wall 160 which is centrally thickened to permit the bolt hole to extend into it. The nut pockets 156, like the pockets 136, are closed at one end by nut stops 162, at the opposite ends of the pockets 156 from those in the pockets 136. See FIG. 12.

The other two bolt holes 155 are displaced 90 from the bolt holes d, and lie on the central plane of the strut wall 126. The 4bolt holes 155 lead to nut pockets 157 formed between the bottom end plate 118 and a wall 161 and defined at the sides by side walls 159 formed as integral extensions of the inner side walls 158 of the pockets 156. A central nut-stop web 163 is formed between the nut pockets 157, and its ends are shaped to position either square nuts or hex nuts in the nut pockets 157. Drain openings 165 connect the nut pockets 157 at opposite sides of the nut stop web 163.

The walls of the insulator 'body 110 are all of substantially the same thickness and substantially uniform throughout, to facilitate molding and to give uniform and rapid curing. Mold draft is desirably provided on those wall faces which extend in the direction of mold separation, and both inside and outside corners on the body may be rounded. The tbody 110 of FIGS. 11-14 is adapted to be molded in a two-part permanent mold which parts in the center plate of the strut wall 124. The bolt holes 134, 154 and 155 may either be bored after molding or formed by retractable inserts in the mold parts. The insulator of FIGS. 11-14 may be used in the same way as described above and as shown in FIG. 1.

For less demanding applications, modified insulators of simplified construction and configuration may -be used. The modified insulator of FIGS. 15 and '16 has only a single -bolt hole at each end and omits the barrier wall interposed between the end plates. Such modification comprises a molded body 210, having a top mounting plate 216 and a bottom mounting plate 218, with strut walls 224 and 226 extending between them and arranged in cruciform relationship. Drain openings 232 extend through the wall 224 adjacent to its intersection with the wall/2,26. Each mounting plate has a single central bolt hole 234 leading to a nut pocket 236 defined by side walls 238 and a bottom Wall 240 and closed at its inner end by a wall 242 which forms a nut stop. The nut pockets open in opposite directions, that is, the one at the top of FIG. 15 opens to the right whereas the one at the bottom opens to the left. The pockets are deep, so that the electrical discharge distance from a nut to a conducting element at the opposite end of the insulator is greater than the length of the insulator. As in other modifications, the entire molded body is adapted to be molded in a two part mold which in this case has its parting plane in the central plane of the strut wall 224.

The modification of FIGS. 17 and 18 utilizes one of the strut walls as a Ibarrier wall interposed between the nut pockets. The insulator of this modification comprises a molded -body 26@ having a top mounting plate 262 and a ybottom mounting plate 264, with one diametric strut wall 266 extending straight in axial bearing relationship between the two end plates, and a second strut wall 268 having its ends ofiset in opposite directions and having an interconnecting oblique midsection. Each end wall is provided with a single bolt hole 270 leading to a nut pocket 272 defined on one side by the end portion 274 of the wall 268 and on the opposite side by a wall 276, and on its inward `face by a horizontal wall 278 which joins the si-de lwalls 274 and 276 and connects with the base of the oblique midsection of the wall 268. The center portion of the horizontal walls 278 may be thickened to provide for extension of the bolt hole 270 into such walls. Drain openings 269 are formed through the wall 266 close to the intersection of the strut wall 268 with the nut pocket walls 278.

The walls 276 and 278 of the nut pocket 272 are relatively shorter than the strut and barrier wall 168, as is shown in FIG. 18, and the nut pockets 272 are fully open at both ends, but nut locating stops like the stops 142 in FIG. 12 may be used at one end of each of the nut pockets 272 if desired.

The body 260, except for the bolt holes 276 is adapted to be molded in a two part mold having a parting plane in the center of the wall 266. As with other modifications, the body is composed of integrally molded walls of similar :sectional thickness, that is, of sufficiently uniform thickness to provide uniform and rapid curing of the molding composition. The configuration of the body composed of such walls ensures that conductive parts at the opposite ends of the body 260, including the nuts in the pocketsl 272, Will be well isolated from each other against electrical discharge or leakage from one to the other.

In all its modifications, the insulator of the present invention can be readily molded in a relatively simple permanent mold, and its walls can readily be made of uniform thickness to provide uniform and quick curing of the molding composition. At the same time, the insulator provides improved electrical and mechanical characteristics fully sufcient to meet the severe requirements for high voltage insulating supports. The mounting plates at the opposite ends of the insulator provide wide-area mounting seats which can be rigidly secured to fixed supports and to heavy conductors by sturdy bolts of standard sizesheld in place with nuts of standard sizes .and shapes which need not be Imolded into the body of the insulator as it is made. Along with these physical and mechanical advantages, the insulator provides good electrical characteristics. Several molding compositions of high insulating value are available, and these may be made non-tracking and arc quenching by the inclusion of substantial proportions of hydrated alumina, and can be made of Ihigh strength by the use of glass fiber and other reinforcing fibrous material. The configuration of the insulators isolates the electrical conductors at one end from those at the other. The lateral disposition and nut-receiving openings of the nut pockets, combined with the use of the strut walls, and especially with the presence of the interposed barrier wall, provides an over surface leakage path between the electrical conducting elements which is exceptionally long in relation to the size of the insulator.

I claim: 1. An electrical insulator for supporting a conductor from a support, comprising a molded body of insulating composition adapted to be connected between a conductor and a support, `said body being substantially composed of integrallyjoined molded sections of similar thickness and including a mounting wall defining an outwardlydisposed mounting seat at one end of the body, said Wall having a bolt hole therethrough to receive a fastening bolt,

walls forming a pocket for a nut on such fastening bolt, including a transverse wall spaced from the mounting wall and positioned to lie between the nut and the opposite end of the body and to extend laterally beyond the nut for electrically shielding the nut from Isuch opposite end,

said nut pocket being open laterally of the body to permit insertion of a nut therein,

mounting means at the opposite end of the body,

land strut walls extending between said mounting means Vat one end and said nut pocket and mounting walls at the other end for supporting the same in spaced relation.

2. An electrical insulator as defined in claim 1 in which said strut walls comprise a first strut wall extending in axial load-bearing relation between said mounting wall and mounting means,

and a stiffening strut wall joined to said first strut wall portion along a line extending betwe-en said mounting means at one end an-d said mounting wall and nut pocket at the other end.

3. An electrical insulator as defined in claim 2 in which said stiffening strut wa'll is integrally joined to the shielding wall of the nut pocket.

4. An electrical insulator as defined in claim 1 in which said strut walls comprise a central cylindrical wall and radial walls joined thereto.

5. An electrical insulator as defined in claim 1 in which said strut walls comprise walls in two intersecting planes.

6. An electrical insulator as defined in claim 1 in which `said strut Walls lare cruciform in cross section.

7. An electrical insulator as defined in claim 1, with the addition of a transverse barrier wal'l carried by Isaid strut walls and interposed between said mounting means at one end and said mounting wall and nut pocket at the other end.

8. An electrical insulator as defined in claim l in which .said pocket-forming walls also include parallel side walls extending between said mounting wall and `said transverse wall.

9. An electrical insulator ,as defined in claim 8 in which said pocket side walls are positioned to hold a nut in the pocket from turning when a bolt is threaded into it.

`10. An -electrical insulator as defined in claim 1, with the addition of `a `self-retaining nut positioned in said nut pocket for fastening engagement by a fastening bolt inserted through said bolt hole,

'said nut having an interfering fit wit-h the nut pocket walls to retain itself in the pocket.

11. An electrical insulator for supporting a conductor from a support, comprising a molded body of insulating compositi-on adapted to be fixedly mounted between a support and a conductor, said body being substantially composed of integrallyjoined molded walls of similar sectional thickness and including a pair .of mounting walls at opposite ends of the body dening outwardly-disposed mounting .seats for mounting engagement with the support and the conductor,

each mounting wall having at least one bolt hole therethrough to receive a fastening bolt,

each such bolt hole leading to a nut pocket formed by and between side walls, said mounting wall, and a shielding wall spaced from the mounting wall and extending transversely between the nut pocket and the opposite end of the body to shield a nut in such pocket from such opposite end,

each nut pocket Ihaving a nut-insertion opening facing to the side of the body, and

strut Walls extending between and supporting in spaced relation -the mounting walls and nut pockets at the opposite ends of the body.

12. An electrical insulator as defined in claim 11, in which said stmt walls comprise intersecting walls extending axially in load-bearing relation between said mounting walls.

13. An electrical insulator as defined in claim 1l, in which said strut walls comprise a cylindrical wall defining a central cavity, and

said body includes a transverse wall closing the bottom of said cavity.

14. An electrical insulator as defined in claim 11, in which said strut walls and nut pocket walls are defined by faces which extend or face in directions away from a single axial transverse mold-parting plane.

1S. An electrical insulator as defined in claim 1l, with the addition of a transverse barrier wall interposed between the mounting plates and nut pockets at one end of the body and those at the other end of the body.

16. An electrical insulator as defined in claim 11, in

which each end plate has a pair of bolt holes spaced in opposite radial directions from the axis of the body, and

the nut pockets for each pair of bolt holes extend in parallel directions transverse to the radial directions of spacing of the holes.

17. An electrical insulator as which the stmt walls of the body include radial wall sections transversely of and joined to the walls of said parallel nut pockets.

18. An electrical insulator as which each end plate has a pair of bolt holes spaced in opposite radial directions from the axis of the body, with both pairs in a common plane, and

one of the end plates has a second pair of bolt holes in a plane at right angles to said common plane.

19. An electrical insulator as defined in claim 11, in

which each nut pocket has a nut-positioning stop at the opposite end thereof from its nut-insertion opening.

20. An electrical insulator as defined in claim 19, in

which the openings of closed-end nut pockets at one end of the body face oppositely from the openings of closed-end pockets at the other end of the body.

21. An electrical insulator as defined in claim 11, in which two nut pockets at opposite ends of the body are parallel, and

the strut walls of the body include a wall which lies on one side of one of said parallel pockets and on the opposite side of the other of said parallel pockets, and has an intermediate portion which stands as an interposed barrier wall between the parallel pockets.

22. An electrical insulator for supporting a conductor from a support, comprising a molded body of insulating composition adapted to be fixedly mounted between a support and conductor, said body having a central axis and being substantially composed of integrally-joined walls of similar sectional thickness and including a mounting wall generally normal to the axis at one end of the body, defining an outwardly disposed mounting seat, and containing a pair of axially extending bolt holes spaced in opposite radial directions from the axis of the body.

a pair of chordal walls projecting axially inward from said mounting wall at the radially inward and outward sides of each bolt hole to define the sides of a nut pocket at the inner end of such bolt hole,

a transverse wall joining each pair of chordal walls to shield a nut in the pocket from conductive parts at the opposite end of the insulator,

and strut walls extending from said mounting-wall and pocket-forming structure to mounting means at the opposite end of the body,

the faces of said mounting wall Iand at least the pocketdefining faces of said chordal and transverse walls being disposed substantially normal to a mold-parting plane, and said strut walls being externally defined by surfaces disposed to permit separation therefrom of a mold which parts at such plane,

whereby said body, including said nut pocket walls may be molded in a mold which parts at such plane.

23. An electrical insulator as defined in claim 22, in which said strut Walls include walls joined to the inner ones defined in claim 16, in

defined in claim 11, in

25. An electrical insulator for supporting a conductor from a support, comprising a molded body of insulating composition adapted to be fixedly mounted between a support and conductor,

said body having a central axis and being substantially composed of integrally-joined walls of similar sectional thickness and including a mounting wall generally normal to the axis at one end ofthe body, defining an outwardly disposed mounting seat, and containing a pair of axially extending bolt holes spaced in opposite radial directions from the,

axis of the body,

a pair of chordal walls projecting axially inward from said mounting Wall and extending parallel to the direction of radial spacing of the bolt holes, at opposite sides of the pair of bolt holes, to define the sides of nut pockets at the inner ends of such bolt holes,

transverse wall sections connecting said chordal walls in position to shield nuts in such pockets from conductive parts at the opposite end of the insulator,

and strut walls integrally joined to said pocket-forming walls and extending to mounting means at the opposite end of the insulator.

26. A high-voltage electrical insulator, comprising a molded body of insulating composition, consisting substantially of integrally-joined molded walls including an end plate at each end forming an outwardly disposed mounting seat for mounting the body to an attached part,

each end plate having a pair of diametrically spaced coplanar bolt holes therethrough for the reception of fastening bolts,

each bolt hole leading to a nut pocket formed by and between side Walls, said end plate, and a shielding wall lying transversely between the nut pocket and the opposite end of the body,

strut walls extending lengthwise of the body and supporting in spaced relation the end plates and nut pockets at opposite ends of the body,

a barrier Wall carried by said strut walls and interposed transversely between the end plates and nut pockets at opposite ends of the body,

the walls of said body being of substantially similar thickness to facilitate molding the same,

said strut walls including iirst radial portions lying in the mold parting plane of the body and second portions normal thereto, all external surfaces of said strut walls and all surfaces of said pocket walls being disposed for separation therefrom of a two-part mold which parts in said parting plane.

27. A high-voltage electrical insulator as defined in claim 26, in which said nut pockets extend in a direction which crosses said parting-plane wall and are spaced on opposite sides of said second strut wall portions.

28. A high-voltage electrical insulator as defined in claim 26, with the addition that one of said end plates has a second pair of diametrically spaced bolt holes, and nut pockets for said second pair of bolt holes are formed at the ends of said second strut Wall portions in alignment with each other, and interconnected by a through passage.

References Cited by the Examiner UNITED STATES PATENTS 1,755,971 4/1930 Smalley 174-165 X 1,793,430 2/1931 Mayer 174-194 X 2,892,014 6/ 1959 Eichelberger 174-212 JOHN F. BURNS, Primary Examiner. 

1. AN ELECTRICAL INSULATOR FOR SUPPORTING A CONDUCTOR FROM A SUPPORT, COMPRISING A MOLDED BODY OF INSULATING COMPOSITION ADAPTED TO BE CONNECTED BETWEEN A CONDUCTOR AND A SUPPORT, SAID BODY BEING SUBSTANTIALLY COMPOSED OF INTEGRALLYJOINED MOLDED SECTIONS OF SIMILAR THICKNESS AND INCLUDINGA MOUNTING WALL DEFINING AN OUTWARDLYDISPOSED MOUNTING SEAT AT ONE END OF THE BODY, SAID WALL HAVING A BOLT HOLE THERETHROUGH TO RECEIVE A FASTENING BOLT, WALLS FORMING A POCKET FOR A NUT ON SUCH FASTENING BOLT, INCLUDING A TRANSVERSE WALL SPACED FROM THE MOUNTING WALL AND POSITIONED TO LIE BETWEEN THE NUT AND THE OPPOSITE END OF THE BODY AND TO EXTEND LATERALLY BEYOND THE NUT FOR ELECTRICALLY SHIELDING THE NUT FROM SUCH OPPOSITE END, SAUD NUT POCKET BEING OPEN LATERALLY OF THE BODY TO PERMIT INSERTION OF A NUT THEREIN, MOUNTING MEANS AT THE OPPOSITE END OF THE BODY, AND STRUT WALLS EXTENDING BETWEEN SAID MOUNTING MEANS AT ONE END AND SAID NUT POCKET AND MOUNTING WALLS AT THE OITHER END FOR SUPPORTING THE SAME IN SPACED RELATION. 